1. Field of the Invention
The present invention relates generally to so-called F-connectors used primarily in the cable television industry to connect coaxial cables to threaded ports, and more particularly to such connectors using O-ring seals to exclude moisture when such connectors are installed outdoors.
2. Description of the Related Art
Coaxial cable F-connectors are often used to terminate a drop cable in a cable television system. The coaxial cable typically includes a center conductor surrounded by a dielectric, in turn surrounded by a conductive foil/grounding braid; the conductive foil/grounding braid is itself surrounded by a protective outer jacket The F-connector is secured over the prepared end of the jacketed coaxial cable, allowing the end of the coaxial cable to be threadedly connected with a threaded port of a terminal block.
Most F-connectors include certain basic components, including a tubular post, a coupling nut, and a cylindrical body member. The tubular post includes a tapered end that slides under the outer jacket of the cable and around the dielectric of the coaxial cable, allowing the central conductor and dielectric portions of the coaxial cable to pass therethrough. The cylindrical body surrounds the tubular post and receives the jacket and outer braid of the cable. The coupling nut serves to secure the F-connector onto a threaded terminal or post.
A variety of methods are known for securing an F-connector over the exposed end of a coaxial cable. For example, crimp style F-connectors are known wherein a crimp sleeve is included as part of the connector body. A special radial crimping tool, having jaws that form a hexagon, is used to radially crimp the crimp sleeve around the outer jacket of the coaxial cable to secure such a crimp style F-connector over the prepared end of the coaxial cable. Examples of such crimp connectors are disclosed within U.S. Pat. No. 4,400,050 to Hayward, assigned to Gilbert Engineering Co., Inc.; and U.S. Pat. No. 4,990,106 to Szegda, assigned to John Mezzalingua Assoc. Inc.
Still another form of F-connector is known wherein an annular compression sleeve is used to secure the F-connector over the prepared end of the cable. Rather than crimping a crimp leeve radially toward the jacket of the coaxial cable, these F-connectors employ a plastic annular compression sleeve that is initially attached to the F-connector, but which is detached therefrom prior to installation of the F-connector. The compression sleeve includes an inner bore for allowing such compression sleeve to be passed over the end of the coaxial cable prior to installation of the F-connector. The F-connector itself is then inserted over the prepared end of the coaxial cable. Next, the compression sleeve is compressed axially along the longitudinal axis of the connector into the body of the connector, simultaneously compressing the jacket of the coaxial cable between the compression sleeve and the tubular post of the connector. An example of such a compression sleeve F-connector is shown in U.S. Pat. No. 4,834,675 to Samchisen and assigned to LRC Electronics, Inc.; such patent discloses a compression sleeve type F-connector known in the industry as "Snap-n-Seal".
No matter the method used to secure the coaxial cable to the F-connector, the F-connector virtually always includes a rotatable nut for securing the F-connector to a threaded port. For F-connectors that are used exclusively indoors, the coupling nut can be free-spinning, as there is no need to create a moisture barrier between the coupling nut and other components of the F-connector. However, it is known in the art that the passage of moisture inside the F-connector can lead to corrosion, increased contact resistance, reduced signal strength, and excessive RF leakage from the connector. Accordingly, when such F-connectors must be used outdoors, those skilled in the art have made various efforts to form a seal between the various components of the F-connector, including the joint between the coupling nut and the tubular post of the F-connector.
For example, the practice of incorporating one or more resilient O-rings between various components of the F-connector has been used to seal out moisture. In U.S. Pat. No. 5,338,225 to Jacobsen, et al., an O-ring is positioned inside the coupling nut just ahead of the tubular post adjacent the internally threaded bore of the nut. However, in this case, the O-ring is contacted by the threaded post and can be degraded by such contact. Moreover, the O-ring is always bearing against both the coupling nut and the end of the tubular post, creating a drag effect that resists rotation of the coupling nut. In addition, such an O-ring does not create any seal between the tubular post and the cylindrical body, nor between the nut and the cylindrical body.
It is also known to dispose an O-ring near the opposite end of the coupling nut, trapped between a rearwardly-directed collar of the nut and the cylindrical body portion of the F-connector; such a structure is shown, for example, in the aforementioned U.S. Pat. No. 4,834,675. During assembly of the connector, the O-ring is pre-compressed between the coupling nut and the cylindrical body to create a seal therebetween; as in the prior example, such an O-ring constantly engages both the nut and the cylindrical body and creates drag therebetween which resists rotation of the nut. Furthermore, the forces created as the coupling nut is tightened over a threaded post or terminal have no impact on the degree of seal created between the coupling nut and the cylindrical body, i.e., further tightening of the coupling nut over the threaded terminal does not increase the amount of compression of the O-ring. Moreover, such an O-ring placement does not create any form of moisture seal as between the nut and the tubular post, nor as between the tubular post and the cylindrical body. In addition, the creation of the rearwardly-directed collar within the coupling nut increases manufacturing costs because the coupling nut must be machined from both ends thereof
In most cases, a coaxial cable service technician threads the coupling nut over a threaded terminal by hand, until the nut is hand-tight. The technician then uses a wrench to make a final turn to secure the nut over the threaded terminal. The continuous drag applied by such O-rings to the coupling nut is a nuisance to service technicians, as compared with indoor-type free-spinning coupling nuts, because it is more difficult to rotate the coupling nut as it is being hand-tightened over the threaded post.
Accordingly, it is an object of the present invention to provide a simple and inexpensive F-connector that includes an O-ring for creating a seal between the coupling nut of the F-connector and at least one other component of the F-connector but which allows the coupling nut to remain free-spinning until the coupling nut begins to tighten about a threaded terminal.
It is another object of the present invention to provide such an F-connector that incorporates an O-ring for simultaneously forming a seal between the nut and the tubular post, and between the nut and the cylindrical body.
It is still another object of the present invention to provide such an F-connector which incorporates an O-ring for simultaneously forming a seal between the nut and the tubular post, and between the tubular post and the cylindrical body.
It is a further object of the present invention to provide such an F-connector which, upon being tightened over a threaded post, simultaneously forms a seal between the nut, the tubular post, and the cylindrical body.
A still further object of the present invention to provide such an F-connector wherein such O-ring lies internal to the F-connector and is not exposed to the threaded terminal over which the coupling nut is ultimately secured.
Yet another object of the present invention is to provide such an F-connector wherein the coupling nut can be machined from only one end thereof during manufacture in order to reduce manufacturing costs.
A further object of the present invention is to provide such an F-connector wherein the final tightening of the coupling nut over the threaded terminal actually serves to compress the O-ing to increase the sealing properties thereof
These and other objects of the present invention will become more apparent to those skilled in the art as the description of the present invention proceeds.